Daily Archives: March 3, 2014

DHCP Server How to Install DHCP Server on CentOS

DHCP stands for Dynamic Host Configuration Protocol. This is a standardized network protocol and is used to automatically assign IP Address to computers on network. It is configured in a Client-Server Environment. DHCP server is the one that assigning IP Addresses to client computers on the network. Each client is assigned a unique IP Address. DHCP server has a number of IP Addresses available in it’s pool, according to requirement of network. Through the DHCP Server IP Addresses are assigned to clients automatically, whenever a computer joins-in through wired or wireless network.

Installation of DHCP Server

Installation of DHCP Server

Best Practice for the deployment of DHCP Server in your Network:

  • Configure the DNS (Domain Name Server) in your network. Installation and configuration of DNS is given at “How to Install DNS Server
  • Assign a static IP address to your DHCP server

Installation of DHCP Server.

# yum install dhcp* -y
# vi /etc/dhcpd.conf
# cat /usr/share/doc/dhcp-4.1.1/dhcpd.conf.sample
# cp /usr/share/doc/dhcp-4.1.1/dhcpd.conf.sample /etc/dhcpd.conf

Edit the /etc/dhcpd/dhcpd.conf file to reflect your desired configuration.

# dhcpd.conf
# Sample configuration file for ISC dhcpd
# option definitions common to all supported networks...
option domain-name "opensourceeducation.net";                      # Change with your DomainName
option domain-name-servers,;         # Change with your DNS IP Addresses 

default-lease-time 600;                                                  # Change with the desired lease time
max-lease-time 7200;                                                     # Change with the maximum desired lease time
# Use this to enble / disable dynamic dns updates globally.
#ddns-update-style none;
# If this DHCP server is the official DHCP server for the local
# network, the authoritative directive should be uncommented.
# Use this to send dhcp log messages to a different log file (you also
# have to hack syslog.conf to complete the redirection).
log-facility local7;                                                     # Option to enable logging to /var/log/messages
# No service will be given on this subnet, but declaring it helps the
# DHCP server to understand the network topology.
#subnet netmask {
# This is a very basic subnet declaration.
subnet netmask   {        # Change with your network IP and Netmask
range;                                 # IP Range to serve - our case from to
option routers;                                                    # Change with IP Address of Gateway
# This declaration allows BOOTP clients to get dynamic addresses,
# which we don't really recommend.
# subnet netmask {
#  range dynamic-bootp;
#  option broadcast-address;
#  option routers rtr-239-32-1.example.org;
# A slightly different configuration for an internal subnet.
# subnet netmask {
#  range;
#  option domain-name-servers ns1.internal.example.org;
#  option domain-name "internal.example.org";
#  option routers;
#  option broadcast-address;
#  default-lease-time 600;
#  max-lease-time 7200;
# Hosts which require special configuration options can be listed in
# host statements.   If no address is specified, the address will be
# allocated dynamically (if possible), but the host-specific information
# will still come from the host declaration.
#host passacaglia {
#  hardware ethernet 0:0:c0:5d:bd:95;
#  filename "vmunix.passacaglia";
#  server-name "toccata.fugue.com";
# Fixed IP addresses can also be specified for hosts.   These addresses
# should not also be listed as being available for dynamic assignment.
# Hosts for which fixed IP addresses have been specified can boot using
# BOOTP or DHCP.   Hosts for which no fixed address is specified can only
# be booted with DHCP, unless there is an address range on the subnet
# to which a BOOTP client is connected which has the dynamic-bootp flag
# set.
host foo2 {                                                                                     # Change with Hostname of host to assign fixed IP Address
hardware ethernet 08:00:27:6B:06:7E;                    # Change with fixed IP host MAC Address
fixed-address;                                                  # Change with the desired IP Address you want to assign to host
# You can declare a class of clients and then do address allocation
# based on that.   The example below shows a case where all clients
# in a certain class get addresses on the 10.17.224/24 subnet, and all
# other clients get addresses on the 10.0.29/24 subnet.
#class "foo" {
#  match if substring (option vendor-class-identifier, 0, 4) = "SUNW";
#shared-network 224-29 {
#  subnet netmask {
#    option routers rtr-224.example.org;
#  }
#  subnet netmask {
#    option routers rtr-29.example.org;
#  }
#  pool {
#    allow members of "foo";
#    range;
#  }
#  pool {
#    deny members of "foo";
#    range;
#  }

now close “dhcpd.conf” file.

Start dhcpd service

# service dhcpd start

Starting dhcpd.... [OK}
Published by:

vSphere 5 How To Install vCenter Server 5.0

VMware vCenter Server is “THE” management system for your VMware vSphere private cloud It’s used to manage your clusters of ESXi servers, configure HA, DRS and vMotion, manage your virtual networks and their interfaces to the physical network.
Its also used to provison storage (maybe even integrated with your SAN) and create virtual machines, including templates and other wonderful things.
For those wanting to find out the new features specifically in vSphere and vCenter server 5 please see here.

Continue reading

Published by:

Configure ISCSI SAN-NAS Target with VMware ESXi Target


Failover and load balancing configuration is crucial when deploying virtual storage solution in your IT environment to achieve optimal resource utilization, maximize throughput, minimize response time, and avoid overload. By using multipath iSCSI connection, you may deliver a high quality and reliable storage service with failover and load balancing capability and it’s also one of the best practices for virtualization environment. All of the Synology NAS with 2 or more network interface are equipped with multipath support on iSCSI Target to help you to deploy failover and load balancing configuration.

 1. Before you start

This article assumes that you have done the following tasks for your DiskStation:

  • Hardware installation for Synology DiskStation.
  • Software installation for Synology DiskStation Manager (DSM, web-based operating system of DiskStation).
  • Creating iSCSI LUNs and Targets.
  • Enable multiple sessions support on your iSCSI Targets, you may refer to here for more information.

  • It is strongly recommended to use MPIO with separate networks (or different subnets) with multiple network interfaces on the iSCSI Initiator and Target.
  • MPIO is only available on Synology NAS with two or more network ports.

2. Setup Virtual Networking on ESXi Sever for iSCSI Connection

This section will guide the administrator in setting up virtual networking on ESXi sever for iSCSI connection.

  1. Open the vSphere Client and proceed to Configuration, Networking and click Add Networking.Nas
  2. Select VMKernel and click Next. Nas
  3. Create a new network switch and select a NIC located on another subnet.
  4. Enter a name for this new network and click Next. Nas
  5. Select Obtain IP settings automatically and click Next. Nas
  6. Confirm all the settings and click Finish to complete the setup. Nas


3. Connect iSCSI Target on the ESXi Server with Multipath

This section will guide the administrator to connect iSCSI Targets on the Synology DiskStation to the ESXi server with multipath support.

  1. Within the Configuration tab, click on Storage Adapters, select the iSCSI Software Adapter and click Properties.
  2. In this example, the iSCSI Initiator is disabled, click Configure to configure the settings of the iSCSI Initiator.
  3. Make sure the iSCSI Initiator is Enabled.
  4. Once the iSCSI Initiator is enabled, click on Dynamic Discovery.
  5. Click Add and enter the primary IP Address of the Synology DiskStation.
  6. Confirm to rescan the Host Bus Adapter.
  7. In Paths, the iSCSI Initiator has detected the target on the Synology DiskStation.
  8. Right click on the Target and click Manage Paths.
  9. Select Round Robin (VMWare).
    Note that within the path management, that the ESXi server is using two paths (via two subnets) to connect to the same iSCSI Target.
Published by:

How to access ESXi Host Vmware through vSphere client

Getting Started with ESXi 5  – Create your first virtual machine


In the previous part of this series, we laid the groundwork for your new ESXi 5-based virtual environment by going through an ESXi 5/VMware Hypervisor installation and installing the vSphere Client software. In this part, we’ll create a virtual machine.

Create your first virtual machine

You now have the key ingredients for virtual machine success. You’ve installed the hypervisor – ESXi 5 – and a management tool – vSphere Client. From here, you can start building virtual machines to meet organizational needs.

Start the vSphere Client by opening Start > All Programs > VMware > VMware Sphere Client. This will open up the vSphere Client login page, shown in Figure 1. On this page, provide the IP address for your ESXi 5 host and also provide the root user name and password that you specified during the setup of your server.

Macintosh HD:Users:scott:Documents:ConvertedImg:Snap10.jpg
Figure 1: Specify the ESXi host and username and password

You will likely receive a security warning like the one shown in Figure 2. This is basically telling you that the SSL certificate being used by the ESXi host can’t be trusted. However, since you just installed the ESXi server, you’re generally sage simply clicking the Ignore button here, although you can also choose to install the certificate to your local certificate store so that you don’t see this message again.

Macintosh HD:Users:scott:Documents:ConvertedImg:Snap11.jpg
Figure 2: It’s safe to ignore this security warning

Once you’ve gained access to the vSphere Client, right click your server IP address and choose New Virtual Machine. Note that the IP address from before and the one you see below are different; I modified some network settings on my ESXi host in between screen shots.

Figure 3: Start the virtual machine creation process

The first question is a simple one: Do you want to use Custom settings for your new virtual machine or do you want to use settings that typically work well based on the operating system you use? For the purposes of this demonstration, I’m choosing the Custom option.

Macintosh HD:Users:scott:Documents:ConvertedImg:Snap12.jpg
Figure 4: Do you want to customize your virtual machine?

Now, provide a unique name for your new virtual machine.

Macintosh HD:Users:scott:Documents:ConvertedImg:Snap13.jpg
Figure 5: Name your new VM

For the purposes of this article, I’m using all local storage; no SAN is involved, although I will include few SAN configurations at some point later on. For now, though, this test virtual machine will be deployed to local storage, as shown in Figure 6. Note that the screen in Figure 6 tells you a bit about the selected storage, such as whether or not thin provisioning is supported.

Macintosh HD:Users:scott:Documents:ConvertedImg:Snap14.jpg
Figure 6: Choose a datastore

VMware has introduced a new version of their virtual machine format – version 8. In addition to enabling a number of new maximums, version 8 also brings with it 3D graphics capability to allow support for Windows Aero and support for high speed USB 3.0 devices. These new hardware capabilities will extend the potential use cases for vSphere, particularly with regard to desktop scenarios. The table below gives you a look at some of the more significant differences between version 7 and version 8 virtual machines. Although version 8 VMs are much more scalable than their version 7 counterparts, version 8 hardware is not supported across all of VMware’s and third party products yet, so choose carefully and only after checking with your vendors.

Some capabilities are dependent on the VMware edition as well. For example, 32-way SMP is available with Enterprise Plus. The table below outlines the high level differences between version 7 and 8 virtual machines without taking into regard edition.


Version 7

Version 8





256 GB

1 TB

3D support









CPU hot add



RAM hot add



Macintosh HD:Users:scott:Documents:ConvertedImg:Snap15.jpg
Figure 7: Choose the virtual hardware version you want to use

The next step is to identify the operating system that will run inside the virtual machine. Your selection will help the client identify the baseline specifications that will be recommended for this new virtual machine. You can see this screen in Figure 8.

Figure 8: Choose your operating system

On the next screen – shown in Figure 9 – you’ll begin to see where ESXi 5 has introduced some changes. Rather than simply assigning a number of cores to a virtual machine, specify the number of virtual sockets you’d like to assign to the machine as well as the number of cores per socket you’d like to assign. The client will calculate the number of cores based on the values you specify.

Macintosh HD:Users:scott:Documents:ConvertedImg:Snap17.jpg
Figure 9: Specify CPU options

Next up, assign RAM to the virtual machine. The virtual machine creation wizard provides you with a number of different recommendations including the minimum recommended RAM based on the operating system you selected, default recommended RAM for this OS and the maximum recommended RAM for this particular operating system. You can see these options outlined in Figure 10.

Macintosh HD:Users:scott:Documents:ConvertedImg:Snap18.jpg
Figure 10: RAM recommendations

Every virtual machine needs one or more network adapters. On the next screen of the wizard, choose the number of NICs you’d like to add to the virtual machine, choose the virtual network to which each NIC should be attached and choose your NIC type.

  • E1000. The E1000 is an emulated version of the Intel 82545EM Gigabit Ethernet adapter. Not all guest operating systems include support for this adapter. Generally, if you’re running a system with Linux kernel 2.4.19 or later, Windows XP Professional x64 Edition and later, and Windows Server 2003 (32-bit) and later, you’ll find E1000 support.
  • VMXNET 2 (Enhanced). Unlike the E1000, the VMXNET adapters do not have physical counterparts and are specifically designed for use in a virtual machine. Once you install VMware Tools, drivers for this network adapter are provided. VMXNET 2 builds on the base VMXNET by adding support for features such as jumbo frames and hardware offload. VMXNET 2 support is provided in the following operating systems:
    o   Windows Server 2003
    o   Windows Small Business Server 2003
    o   Windows XP Pro 32-bit
    o   Red Hat Enterprise Linux 5.0
    o   SUSE Linux Enterprise 10
    o   Red Hat Enterprise Linux 4.0 64-bit
    o   Ubuntu Linux 64-bit
  • VMXNET 3. VMXNET 3 is not simply a next version of VMXNET 2. It’s a new adapter type that includes all of the features of both VMXNET and VMXNET 2 but adds additional features including IPv6 offloads and multiqueue support. VMXNET 3 is supported in the following guest operating systems (refer to VMware documentation for limitations that may be specific to each operation system):
    o   Microsoft Windows XP,7, 2003, 2003 R2, 2008, and 2008 R2
    o   Red Hat Enterprise Linux 5.0 and later
    o   SUSE Linux Enterprise Server 10 and later
    o   Asianux 3 and later
    o   Debian 4
    o   Ubuntu 7.04 and later
    o   Sun Solaris 10 U4 and later

Macintosh HD:Users:scott:Documents:ConvertedImg:Snap20.jpg
Figure 11: Choose a network adapter type

Although the network adapter type is an important selection for your new virtual machine, your choice of SCSI controller will likely have more significant performance implications. This selection is made on the next screen of the virtual machine creation wizard, as shown in Figure 12.

  • BusLogic Parallel. This is the default selection for older operating systems.
  • LSI Logic Parallel. This is akin to a traditional parallel SCSI adapter and is not suitable for all purposes, but is generally compatible with guest operating systems.
  • LSI Logic SAS. This is the default for Windows-based guest operating systems.
  • VMware Paravirtual. As is the case with the VMXNET series of Ethernet adapters, the VMware Paravirtual SCSI (PVSCSI) adapter is designed for virtual hardware, but it has some limitations, such as a restricted list of supported guest operating systems.

Macintosh HD:Users:scott:Documents:ConvertedImg:Snap21.jpg
Figure 12: Choose a SCSI controller type

Next up, choose your virtual disk. You can create a brand new virtual disk, as you can see in Figure 13 is the route I’ve taken, use an existing disk, create a raw device mapping (RDM) or not create a disk at all.

Macintosh HD:Users:scott:Documents:ConvertedImg:Snap22.jpg
Figure 13: Select a disk

Since I’ve chosen to create a new virtual disk, the wizard’s next step is to provide me – Figure 14 – with the options that I need to carry out that wish.

On this screen, I’m asked three questions:

  • Size of the new virtual disk
  • Provisioning type
    o   Thick Provision Lazy Zeroed. Fully allocated space for the new virtual disk and wipes it of previous data.
    o   Thick Provision Eager Zeroed. Fully allocates, wipes, and zeroes out allocated space on the new virtual disk. Some applications require the use of Eager Zeroed disks. On the surface, it would seem that this type of disk provides the best performance since space is already allocated and prepared, but some testing has shown that the performance benefits may not be substantial.
    o   Thin Provision. Disk space is not immediately allocated to the disk. It’s allocated on demand with the upper space limit being the specified size of the virtual disk. There are enormous space benefits to be had with thin provisioning, but it also requires you to keep a careful eye on storage to avoid accidentally overprovisioning and running out of space.
  • Virtual disk location

Macintosh HD:Users:scott:Documents:ConvertedImg:Snap23.jpg
Figure 14: Choose a location for the new virtual disk

If you like, you can make advanced changes to the disk configuration on the next page of the wizard, shown in Figure 15.

Macintosh HD:Users:scott:Documents:ConvertedImg:Snap24.jpg
Figure 15: Advanced disk options

Published by:

How To Install VMware ESXi 5.5 HyperVisor

VMware ESXi 5.5 Step by Step Install Guide



Here is a guide I put together on installing ESXi 5.5 on your host.



Download the ISO from VMware’s website. In order to do this you will need to have a VMware account and register for the free trial. One you have everything select the ESXi 5.5 ISO hypervisior and select manual download



Once the ISO has been downloaded burn to a DVD or if creating a nested version off ESXi select the Iso file location on your machine.


Insert the DVD into the machine and boot off of that device


Once boot up has begun you will see a screen shown below that will automatically load up into the esxi 5.5 installer. You can Hit “Enter” or wait the 10 second time out to begin loading up the installer.



After the setup has finished loading you will be able to start the installation, Hit “Enter” to being installing ESXi 5.5


Accept the User Agreement by hitting “F11”


Now your system will be scanned for hardware and storage


In my lab I’m installing ESXi on a VM, On this next window you can select the storage to install ESXi on. If you’re installing on a physical server you may want to consider using a 4GB usb flash disk. Once you have selected the proper storage hit “Enter” to continue


Next select your language and hit “Enter” to continue


Next we will be setting the Root password. This is your only way of accessing the host until it has been joined vCenter. Make sure you do not forget this password. Once you have created your password hit “Enter” to continue


The system will once again scan for additional system information making sure your system meets the minimum requirements. For my lab here it told me I did not have enough Ram and I had to add more before continuing.


Before continuing with the install you will get a warning message that the selected storage will be repartitioned meaning all data will be destroyed. Hit “F11” to continue


Now the installation has begun copying files to your storage location


You are finished, Make sure to remove the installation DVD or unmounts it from your VM before rebooting. Hit “Enter” to finish and reboot the host.





Once rebooted the ESXi host will load up and you can now begin to configure and administer this host



Published by: